Tidal effect on organic primary productivity in a coastal lagoon of Ballenas Channel, Gulf of Californla

Phytoplankton organic primary productivity (POP) and nutrient time series were generated in a coastal lagoon of the Gulf of California from 6 to 12 August 1986 to estimate the influence of Ballenas Channel during spring and neap tides. Ocean water temperature and salinity varied from 26 to 30°C and from 35.54 to 35.63%0, respectively. Oxygen was unsaturated at 85% in more than 70% of the data collected. Values of supersaturated oxygen were obtained during daylight hours only, which increased during neap tides due to the conditioning of the phytoplankton, resulting in greater photosynthesis. It can be inferred from the marked unsaturation that this is an area of high oxygen consumption and CO2 production. The nutrients (nitrate, phosphate and silicate), chlorophyll a and POP show high values, similar to coastal lagoons of the Pacific coast of Baja California in upwelling conditions. POP maximums were as high as 80 mgC·m–3·h–1 in neap tides. It is deduced from the calculated photosynthetic quotient (PQ) and POP that photosynthesis is supported mainly by nitrates. Based on the 14C method, the assimilation ratio varied from 10 to 25 mgC·mgCha–1·h–1. These values are close to the theoretical maximums reported; however, the assimilation ratio using the oxygen method and PQ = 1.25 varied from 1.6 to 35.6 mgC·mgCha–1·h–1 and, with the calculated PQ, it varied from 1.0 to 7.2 mgC·mgCha–1·h–1. It is also deduced that this coastal lagoon is greatly influenced by the nutrient concentrations (mainly nitrate and silicate) from Ballenas Channel during spring tides. There is also an important increment of POP during neap tides

Photosynthetic quotients in the Gulf of California during autumn 1987 in the central region and spring 1989 in Puerto Don Juan

In order to study the photosynthetic quotient variability (PQ = O2/14CO2) and to infer the relative contribution of new production in the Gulf of California, simultaneous determinations of photosynthesis were made using the 14C and oxygen techniques. Additionally, nutrient concentration was determined in the central region during autumn 1987 and during spring 1989 in a coastal lagoon in the same region. In both areas nutrient distribution suggests consumption by photosynthesis within the euphotic zone. The PQ integrated in the water column for single experiments goes from 1.43 ± 0.29 to 4.01 ± 0.33 in the central region and from 1.32 ± 0.22 to 3.08 ± 0.38 in the coastal lagoon Puerto Don Juan and does not differ from the PQ calculated for each depth. Calculated PQ values indicate the presence of NO3– during photosynthesis. The global PQ for all the experiments in both study areas was calculated by regression analysis for the central region (1.56 ± 0.45) and Puerto Don Juan (1.68 ± 0.56), suggesting NO3– influence during both seasons in both areas. A greater relative contribution of new production than regenerated production in both areas of the Gulf of California is inferred

Temporal variation of total carbohydrates, polysaccharides, monosaccharides and microbial metabolic activity in Estero de Punta Banda, Mexico

The concentration of total carbohydrates (CHOT), monosaccharides (MCHO) and polysaccharides (PCHO) was measured in situ using the MBTH technique. Samples were taken in diel cycles inside and outside a mesocosm in order to elucidate the pattern of production and consumption. Six seasonal samplings were conducted in one year during spring tides. Changes in the different carbohydrate fractions were compared to temperature, chlorophyll a, dissolved oxygen, gross production bacterial biomass and planktonic community respiration. Outside the mesocosm, the changes in these variables are mainly intluenced by advective processes. A linear, inverse relationship between PCHO and MCHO is found, suggesting microbial degradation. Also, CHOT concentrations ate directly proportional to PCHO concentrations. The variability of the MCHO concentration is mainly esplained by chlorophyll a, suggesting a phytoplanktonic origin. On the other hand, PCHO are mainly explained by the tide and temperature. indicating their possible origin in the macrophytes of the marsh area. The presence of carbohydrate-like organic matter is detected by the MBTH technique masking the diurnal variations of- the carbohydrates outside the mesocosm. Outside the mesocosm, advective processes interfere with the interpretation of diel cycles of the MCHO, PCHO, and CHOT concentrations. However, inside the mesocosm it is possible to clearly observe carbohydrate degrading processes on a seasonal scale

Sistema Fotoelectrónico para titulaciones de oxígeno disuelto con alta precisión y su aplicación en oceanografía biológica

The present paper describes the assemblage and emplayment of a portable and energetically low-demanding apparatus, designed to measure dissolved oxygen concentrations in the water. Its underlying technique is based in the absortion of light (wavelength=355nm) by the triodate fraction of a Winkler titrating solution. The proposed desin has allowed for an acceptable precission in water sample and standart solution itrations (0.1% ans 0.09 to 0.04%, respectively). These results equal those reported by other workers using similar instruments. Resolution and sensibility were assessed by mens of a 14C and 02 photosynthesis experiment; good accordance was found in between both sets of data, given the usage of a suitable photosynthetical quotient (PQ). Simplicity and sturdiness make this instrument very suitable for outdoor data gathering, as is often the case in the course of planctonic productivity and water column metabolism routines.Se describe la construcción y empleo de un sistema portátil y de bajo consumo de energía para la medición de oxígeno disuelto en agua. Basado en la técnica de detección de la absorción de energía lumínica de 355 nm por el triyoduro, este aparato permite la determinación del punto final de la titulación Winkler con gran precisión: 0.1% en muestras de agua y 0.09 a 0.04% en estándares, misma que se sitúa en el orden de la reportada en la literatura por autores y usuarios de instrumentos similares. La resolución y sensibilidad del aparato fueron probadas mediante un experimento de fotosíntesis con 14C y oxígeno, encontrando buena concordancia entre ambas técnicas cuando un valor adecuado del cociente fotosintético (PQ).Este aparato de fácil construcción y adecuado para trabajos en el campo es muy útil en estudios de producción planctónica y metabolismo en la columna de agua

Effect of turbulent kinetic energy on the spatial distribution of chlorophyll a in a small coastal lagoon

In order to observe the effect of turbulent kinetic energy (TKE) on the spatial distribution of chlorophyll a, four spatial variations were analysed (two during high and two during low tide) on 15 and 16 April, 1989 in Puerto Don Juan. Observations were made of buoy drifts and tidal height, and surface water samples were taken at 20 stations to determine chlorophyll a concentration in each variation. A pattern for ebb conditions is inferred, which shows a direct relationship between a smooth bottom slope and a high concentration of chlorophyll a. For flow conditions, the relationship is inverse. We suggest that the higher concentrations of chlorophyll a are due to a simple mechanical process of accumulation in areas with certain morphological characteristics that attenuate the TKE. That is, the speed of transport of the phytoplankton that enters the lagoon decreases on reaching areas of low TKE, causing stagnation of the particles. This long-term pattern produces high concentrations in the inner part of the lagoon, resulting in higher concentrations of chlorophyll a at the innermost stations. When the tide begins to ebb, these patches of high concentration are transported to the outer part of the lagoon

The Colorado River Delta: A high primary productivity ecosystem

The construction of major dams in the Colorado River has produced a drastic effect on the amount of fresh water entering the Colorado River Delta. After 1935 there was a dramatic decrease in fresh-water input, causing ecological impacts and a decrease of organisms in the natural habitat. We carried out six spatial samplings during a period of no fresh-water inflow to the delta, in June, August and November 1989, and February, April and June 1990; during each sampling, a 24-hour time series was conducted at one station and seawater samples were taken every two hours. Also, in May 1991 we carried out an eight-day time series, taking samples of seawater at 08:00, 12:00 and 16:00 hours. The objective was to estimate phytoplankton abundance, chlorophyll concentration and primary productivity during a period of no fresh-water input. In the spatial distribution, the chlorophyll a concentrations and phytoplankton abundance were higher on the Baja California side than on the Sonora side, with concentrations of 2.6–18.2 mg m–3 and 1.8–12.7 mg m–3 and of 274 and 166 cells mL–1, respectively. In the time series, the dinoflagellates were more abundant than the diatoms. The primary production showed a tendency to decrease from August 1989 to June 1990, with values of 15.0 to 0.5 mgC m–1. The primary productivity values in the time series presented a tendency to increase during the tide transition, reaching values of 76 mgC m–1. The variations of chlorophyll concentration, phytoplankton abundance and primary productivity were strongly influenced by the effects caused by the tidal currents

Primary productivity and chlorophyll a in the central part of the Gulf of California (Autumn 1987)

 A cruise was carried out in the central part of the Gulf of California from 27 October to 7 November, 1987. Seawater samples were taken from 0, 5, 15, 25 and 50 m depth to determine chlorophyll a and phaeophytin a content at 22 stations. Six experiments of productivity in the euphotic zone and one experiment of photosynthesis-irradiante were generated. The vertical profile of chlorophyll a in Ballenas Channel was more homogeneous at the southern end of the channel due to mixing and the increase in the euphotic zone. In the region of the islands, the distribution of chlorophyll a was more variable due to mixing processes that occur in that area. In the southern part of the study area, chlorophyll a decreased from the coast to the open sea. Similar assimilation numbers and photosynthetic rates were obtained with samples collected at 22 and 60% of surface irradiance in one productivity versus irradiante (P-E) experiment in Ballenas Channel. It is inferred that vertical transport of phytoplankton occurred in the water column. Surface primary productivity values were three to four times higher in the northern part of the study area than in the southern part, whereas integrated productivity values were one to two times higher in the northern part